While much is known regarding the chemical pathways involved in platelet activation and clot formation, little is generally known about the physical and mechanical interactions between platelets and fibrin. During clot formation, activated platelets from the blood attach to and interact with fibrin polymers that form; physically, the platelets contract against the fibrin scaffolds. This contraction by platelets changes the mechanical properties of the clot itself. Mechanical changes in the clot are believed to underlie some of the pathophysiology of thrombotic conditions such as cardiovascular disease and stroke. However, current methods generally only allow for the measurement of large scale, bulk clot retraction, obscuring the actually behavior of the individual or small numbers of platelets during clot formation.